FIG. 11 shows a cross-sectional view of a radiation detection device described in the Japanese Patent 312675. In FIG. 12, reference numeral 110 denotes a scintillator panel (referred to also as the “fluorescent plate”) comprising: a scintillator layer 113 constituted of a scintillator material crystallized into a columnar shape; a substrate 111 for supporting the scintillator layer 113; a reflective layer 112 constituted of an aluminum thin film which reflects light converted by the scintillator layer 113 on the side of a sensor panel (referred to also as the “photoelectric conversion panel”) described later; a protective layer 115 for protecting the layer; and a protective layer 114 formed of an organic resin to protect the scintillator layer 113 and the like from outside air.
Moreover, in FIG. 11, reference numeral 100 denotes a photoelectric conversion panel comprising: a glass substrate 101; a photoelectric conversion element portion 102 constituted of a photo sensor and TFT using amorphous silicon; and a protective layer 104 which protects the photoelectric conversion element portion 102 and which is formed of silicon nitride and the like.
Furthermore, the photoelectric conversion panel 100 is bonded to the scintillator panel 110 by an adhesive layer 120 formed of a transparent adhesive, and the periphery is sealed by a sealing material 140. Here, a thickness of each layer which transmits the light needs to be correctly controlled in order to prevent resolution from being scattered. Especially, the adhesive layer 120 needs to be prevented from being excessively thick. The adhesive layer 120 is applied between the sensor panel 100 and the scintillator panel 110, thereafter they are entirely drawn with a roller, and the layer is bonded to the panel in such a manner that the adhesive layer 120 is prevented from being thickened.
X-rays which have fallen from an upper part in FIG. 11 pass through the substrate 111, reflective layer 112, and protective layer 115, and is absorbed by the scintillator layer 113, and thereafter the scintillator layer 113 emits visible light. Since the visible light travels through the scintillator layer 113 on the sensor panel 100 side, the light enters the photoelectric conversion element portion 102 through the protective layer 114, adhesive layer 120, and protective layer 104 without diffusing.
In the photoelectric conversion element portion 102, the incident visible light is converted into an electric signal, and read to the outside through a wiring portion 103 by switching. In this manner, incident X-ray information is converted into a two-dimensional digital image by the X-ray detection device shown in FIG. 12.
Here, alkali halide scintillator materials having columnar crystal structures have been used as materials of the scintillator layer 113 for a high-sensitivity X-ray detection device. Among the materials, especially cesium iodide (CsI):Tl is used whose emission wavelength matches a sensitivity wavelength of the photoelectric conversion element. A maximum emission wavelength of CsI:Tl is 500 nm to 600 nm. As a method of forming the alkali halide scintillator material into a film, a vapor deposition process is used. For example, CsI:Tl is obtained by codeposition of cesium iodide (CsI) and thallium iodide (TlI) on the substrate 111. It is known that the thickness of the scintillator layer 113 having the columnar crystal structure is, for example, 200 μm to 450 μm. In the alkali halide scintillator material obtained by the vapor deposition, the scintillator layer needs to be heated at a temperature of 200 to 250° C. in order to raise light emission after a vapor deposition step.
When the scintillator layer 113 is crystallized into the columnar shape, projective portions 116 having a height of several tens to hundreds of micrometers from the surface are formed by partially generated abnormal growth by dust, splash at a vapor deposition time, fluctuations of surface roughness of the substrate 111 and the like. This projective portion 116 forms a concave/convex portion constituted of a convex portion and a peripheral concave portion, and causes problems: 1) destruction of the element; 2) destruction of the protective film; 3) mixing of bubbles; 4) drop of resolution and the like. As countermeasures, it has been described that Japanese Patent Application Laid-Open Nos. 2003-66196 and 2002-243859 that the scintillator material is formed, and thereafter irregularities on the surface are reduced to solve the above-described problems. As a result, the irregularities of the projective portions 116 shown in FIG. 12 are reduced, and projective portions 117 in which the irregularities have been corrected are formed as shown in FIG. 12.